Irradiation Methods for Accurate Dose Delivery to Postoperative Keloid Scars With Minimal Normal Tissue Exposure Using TomoTherapy: A Phantom Study

Background/Aim: We aimed to clarify the TomoTherapy irradiation method for accurate dose delivery to the postoperative ear keloid with minimal exposure. Materials and Methods: An electron beam of Elekta synergy and static and helical photon beams of TomoTherapy were delivered to the auricle and lobe of an anthropomorphic phantom compensated using a soft rubber bolus. The doses to the ear surface and the eyeballs and thyroid were measured using radiochromic film and glass dosimeters, respectively. Results: Using static, helical, and electron beams, the respective doses to the ear surface were 97.9%, 103.0%, and 91.7% of the prescribed dose; the respective doses to the thyroid were 0.6, 0.8, and 2.4 cGy; the respective doses to the left eyeball were 3.3, 6.9, and 2.7 cGy. Conclusion: The static beam of the TomoTherapy can be safely used for treating ear keloids, while ensuring target dose. The helical photon beam spreads out the low-dose exposure.